RF circuit module

ABSTRACT

A module for radio frequency signal circuits includes an electrically conductive housing. Coax connectors are secured to the rear face of the housing. A circuit board is contained within the interior spaced between sidewalls of the housing. A ground side of the circuit board includes a layer of electrically conductive material which is electrically connected to the housing. Coax cables extend within the interior of the housing from the coax connectors and between the ground side of the circuit board and an opposing sidewall. An opposite side of the circuit board contains circuit components inter-connected with one another through a plurality of circuit paths.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention pertains to circuits for broad-band RF systems.More particularly, this invention pertains to modular RF (radiofrequency) circuit components.

[0003] 2. Description of the Prior Art

[0004] In the telecommunications industry and more particularly in thevideo transmission industry, broad-band radio frequency (RF) signals(i.e., 5 MHz to 1 GHz) are carried over coax conductors from a headendto consumers. At the headend of the system, numerous signals aremanipulated to achieve a wide variety of functions and objectives. Forexample, signals carried on numerous coax cables may be combined onto asingle coax conductor. Similarly, a signal on a main coax conductor maybe divided into a plurality of signals carried on branch coaxconductors. Additionally, signals may be added or removed from a mainconductor through directional couplers or the like.

[0005] In addition to combining, splitting, diverting or adding signals,the headend will also include apparatus for modifying signals. Forexample, in order to adequately tune the system, it may be desirable toprovide attenuators or the like to attenuate a signal to a desiredlevel. Further, as a broadband RF signal is carried over a length ofcable, the high frequency range of the signal may be attenuated morethan a low frequency range of the signal. As a result, equalizers areutilized to modify the signal to have a level intensity throughout itsfrequency range.

[0006] Throughout the system, performance characteristics are critical.For example, a common performance criteria is to maintain the flatnessof a signal. Flatness refers to maintaining a level intensity of asignal throughout its frequency range. For example, if the signal isattenuated by 2 dB at 1 Ghz, then it is desirable that the signal beattenuated at 2 dB at the 5 Mhz frequency. Further, the system needs tobe tuned for impedance matching.

[0007] Prior art headends include a wide variety of devices toaccommodate and accomplish the functions described above. It isdesirable to provide an apparatus to accommodate the various functionsrequired at the headend through a modular construction to permit ease ofmaintenance and cable management in a headend. Such a device mustaccommodate the performance characteristics of the headend whilepermitting the modular construction to enhance the cable management andorganization of a headend.

SUMMARY OF THE INVENTION

[0008] According to a preferred embodiment of the present invention, amodule is provided for containing a circuit for performing discretefunctions on a radio frequency signal. The module comprises a housing ofelectrically conductive material. The housing has a front face and anopposite rear face. The front face and rear face are separated byopposite sidewalls and opposite end walls. A plurality of coaxconnectors are secured to the rear face with an outer shield of theconnectors electrically connected to the housing. A circuit board iscontained within the interior. The circuit board is generally parallelto and spaced between the sidewalls. The circuit board has a componentside and a ground side. The ground side includes a layer of electricallyconductive material which is electrically connected to the housing. Aplurality of coax cable connection locations are provided on the groundside of the circuit board. Each of the coax cable connections includes aground connection for connecting ground shields of coax cables to thelayer of electrically conductive material. The component side of thecircuit board includes a plurality of circuit components interconnectedwith one another and with the coax cable connection locations through aplurality of circuit paths. A plurality of coax cables are disposedwithin the interior and connected to individual ones of the coaxconnectors and the coax cable connection locations. Each of the coaxcables has a ground shield connected to the outer shields of theconnectors and to the ground connections of the coax cable connectionlocations. A plurality of cables are routed for the cables to bedisposed between the ground side of the circuit board and the opposingsidewall of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a bottom end, front face and right sidewall perspectiveview of one embodiment of a module according to the present inventionshown in exploded view (with internal cables omitted);

[0010]FIG. 2 is a left side plan view of the module of FIG. 1;

[0011]FIG. 3 is a right side plan view of the module of FIG. 1;

[0012]FIG. 4 is a front elevation view of the module of FIG. 1;

[0013]FIG. 5 is a rear elevation view of the module of FIG. 1;

[0014]FIG. 6 is a bottom end view of the module of FIG. 1;

[0015]FIG. 7 is a top end view of the module of FIG. 1;

[0016]FIG. 8 is a rear, right side and top end exploded view of themodule of FIG. 1 with a cover removed;

[0017]FIG. 9 is a perspective view of internal components of the moduleof FIG. 1;

[0018]FIG. 9A is a top plan view of a printed circuit board and attachedcomponents;

[0019]FIG. 10 is an opposite side plan view of the components of FIG. 9;

[0020]FIG. 11 is a side cross-sectional view of the module of FIG. 1;

[0021]FIG. 12 is a view similar to that of FIG. 1 showing in explodedformat an alternative embodiment of the present invention;

[0022]FIG. 13 is a right side plan view of the module of FIG. 12;

[0023]FIG. 14 is a left side plan view of the module of FIG. 12;

[0024]FIG. 15 is a front elevation view of the module of FIG. 12;

[0025]FIG. 16 is a rear elevation view of the module of FIG. 12;

[0026]FIG. 17 is a bottom end view of the module of FIG. 12;

[0027]FIG. 18 is a top end view of the module of FIG. 12;

[0028]FIG. 19 is a bottom end, front face and right sidewall perspectiveview of a third embodiment of a module according to the presentinvention shown in exploded view (with internal cables omitted);

[0029]FIG. 20 is a right side plan view of the module of FIG. 19;

[0030]FIG. 21 is a left side plan view of the module of FIG. 19;

[0031]FIG. 22 is a front elevation view of the module of FIG. 19;

[0032]FIG. 23 is a rear elevation view of the module of FIG. 19;

[0033]FIG. 24 is a bottom end view of the module of FIG. 19;

[0034]FIG. 25 is a top end view of the module of FIG. 19;

[0035]FIG. 26 is a perspective view of a first embodiment of a chassisfor holding modules according to the present invention;

[0036]FIG. 27 is a perspective view of a second embodiment of a chassisfor holding modules of the present invention; and

[0037]FIG. 28 is a perspective view of a third embodiment of a chassisfor holding modules of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038] Referring now to the several drawing figures in which identicalelements are numbered identically throughout, a description of thepreferred embodiment of the present invention will now be provided.

[0039] With initial reference to FIGS. 1 through 11, a module 10according to the present invention will be described for use as asplitter/combiner module for splitting a main signal into a plurality ofbranch signals or, alternatively, combining a plurality of branchsignals into a common main signal. The module 10 includes a housinghaving a front face 14, a rear face 16. The front face and rear face 14,16 are separated by opposing sidewalls 18, 20 and opposite end walls 22,24. The housing 12 is formed of electrically conductive material.Preferably, the material is nickel-plated aluminum.

[0040] Sidewall 18 and end walls 22, 24 are integrally formed as a boxconfiguration with walls 22, 24 having inwardly protruding peripheralledge 26. Rear wall 16 is secured to walls 18, 22, 24 by screws 28. Thesidewall 20 is fastened to the ledge 26 by a plurality of screws 28received in aligned bolt holes 30 of sidewall 20 and threaded bolt holes32 on the peripheral ledge.

[0041] The sidewall 20 is sized to have a length greater than thelongitudinal dimension between walls 22, 24 such that ends 20 a, 20 bextend beyond ends 22, 24 as flanges for purposes that will bedescribed.

[0042] The front cover 14 includes extending edges 14 a, 14 b whichextend beyond ends 22, 24. The front cover further has an internal ledge34 (shown in FIGS. 1, 8 and 11) on an interior surface of the cover 14.The ledge 34 is sized to extend into the interior of the housing whenthe front cover 14 is attached to the housing.

[0043] The front cover 14 and sidewall 20 are secured to the housing bythe screws 28 received within aligned bolt holes. The screws 28 arepreferably positioned at one-half inch on-center spacings to prevent EMIleakage as is conventional.

[0044] The front cover 14 includes a plurality of openings 36 thefunction of which will be described with the openings 36 arrangedlinearly along the face 14. Similarly, the front cover 14 includes anopening 38 sized to pass a coax connector 41 for purposes that willbecome apparent.

[0045] A plurality of coax connectors 40-0 through 40-8 are secured tothe rear face 16. Each of the coax connectors is identical. Suchconnectors are conventional and include a central conductor surroundedby a grounded shield. The grounded shields of the coax conductors are indirect physical and electrical contact with the electrically conductivematerial of the rear face 16.

[0046] Contained within the interior of the housing 12 is a printedcircuit board 44. The printed circuit board 44 is supported on posts 42by screws 43. The posts 42 are electrically conductive and connected towall 18. The printed circuit board 44 includes a component side 44 a anda ground side 44 b (see FIG. 9). The ground side 44 b opposes the wall18 and the component side 44 a opposes wall 20. The printed circuitboard 44 is maintained in parallel, spaced relation between the walls18, 20 by supports 42.

[0047] A layer 44 c (FIG. 9) of electrically conductive material (suchas a sheet layer of copper) is provided on the exterior surface ofsurface 44 b.

[0048] A plurality of coax cable connection locations 48-0 through 48-8are provided on the ground side 44 b of the printed circuit board 44.Each of the coax cable connection locations 48-0 through 48-8 include aground connection for connecting the ground shields of a coax cable tothe conductive layer 44 c.

[0049] A plurality of circuit components are disposed on the componentside 44 a of the printed circuit board 44. In the embodiment shown, thecomponents include a solid state directional coupler 50 and three solidstate splitter/combiners 52-1, 52-2 and 52-3.

[0050] It will be appreciated that a solid state directional coupler 50is a commercially available item, and an example of such is a 20 dBcoupler Product No. CPL/20BE-08A3 sold by TRAK Microwave, 4726Eisenhower Blvd., Tampa, Fla. 33634-6391. Similarly, solid statesplitter/combiners 52-2 through 52-3 are commercially availableone-by-four splitters and examples of such are Product No. SPL/4BE-53Dsold by TRAK Microwave. Splitter/combiner 52-1 is a one-by-two splittersuch as Product No. SPL/2BE-53D of TRAK Microwave.

[0051] The splitter/combiners each receive a signal and divide an RFsignal into two signals of equal strength. Splitter/combiners 52-2 and52-1 are electrically connected in series. Similarly, splitter 52-3 isconnected in series with splitter 52-1 such that splitter 52-3 isconnected in parallel to splitter 52-2.

[0052] The electrical connection of the components 50 and 52-1 through52-3 is provided through a plurality of circuit paths 53 (FIG. 9A)contained on the surface 44 a where the circuit paths connect thecomponents 50, 52-1 and 52-3 with the coax connection locations 48-0through 48-8. The circuit paths connect the components and theconnection locations such that connectors 40-0 is connected to thedirectional coupler 50 with a portion of the signal diverted from thedirectional coupler 50 to the coax monitor connector 41 through cable41-1. Preferably, coupler 50 provides a -20 dB monitor signal.

[0053] The main signal from the directional coupler 50 is passed to thesplitter/combiner 52-1 which divides the main signal into two signalswith one passed along the circuit paths to splitter/combiner 52-2 andthe other passed to splitter/combiner 52-3. Each of splitters 52-2 and52-3 split a signal into four signals. resulting in a total of eightbranch signals passed to connection locations 48-1 through 48-8.

[0054] In the preceding paragraph, a signal is described as coming intothe directional coupler from connector 40-0 and then eventually splitand passed to connectors 40-1 through 40-8. With the directional coupler50 arranged in the schematic shown of FIG. 3, such a signal flow pathwould result in losing a monitor function at monitor port 41. With thisschematic shown in FIG. 3, signals passed into connectors 40-1 through40-8 are attenuated and combined to a main signal which is then passedthrough directional coupler 50 to OUT port 40-0. A portion of the mainsignal is then passed from the directional coupler 50 to the monitorport 41 so that the signal may be monitored. If it is desirable to passa signal into connector 40-1 for division into branch signalsdistributed to connectors 40-1 through 40-8, a different directionalcoupler 50 can be provided such that a signal from connector 40-0 can bemonitored at port 41.

[0055] Before the branch signals are passed to the connection locations,they are passed through attenuator components. Each of the attenuatorcomponents is identical and includes a base member 60-1 through 60-8which is secured to the component side 44 a of the printed circuit board44 along a leading edge 44 d of the printed circuit board and with thebase members 60-1 through 60-8 arranged in a linear array.

[0056] A plurality of the attenuator plugs 64-1 through 64-8 areprovided to be releasably connected to individual ones of the basemember 60-1 through 60-8. The attenuator plugs 64-1 through 64-8 providean attenuation to a signal to each of the branch circuits being sent toconnectors 40-1 through connectors 40-8.

[0057] Attenuator plugs and base members are commercially availableitems such as those sold as Product No. F-7520-A (for a 20 dBattenuator) through Communication Associates 1750 T-′ Coleman Road,Anniston, Ala. 36207. The plugs 64-1-64-8 can be individually selectedto provide a discrete amount of attenuation to a signal. For example, a“zero” plug can be inserted into a base member to provide 0 dBattenuation. Alternatively, at an option of a technician, the 0 dB plugmay be replaced with a 15 dB plug to provide 15 dB attenuation to asignal. As a result, each of the branch circuits can be individuallyprovided with a unique attenuation selected at an option of atechnician. The holes 36 on the front face 14 are arranged and sizedsuch that each of the attenuator plugs extends through individual onesof the holes 36 to be grasped by an operator. As a result, an operatorcan remove and replace an attenuator plug without needing access to theinterior of the housing 12.

[0058] To provide EMI leakage protection, the front face 14 is providedwith a removable cover 100 surrounding the array of holes 36. Adeformable, conductive seal 102 (silicon gasket impregnated with silverparticles) is provided between the cover 100 and face 14. Threadedconnections 104 on the cover 100 are aligned with threaded holes on thestandoff posts 106 such that the cover 100 can be secured to the face 14by turning the threaded connectors 104 into the standoff posts 106. Asthe threaded connection 104 is tightened, the edge of the cover 100compresses into the seal 102 to thereby compress the seal 102 againstthe face 14 to provide an effective EMI seal.

[0059] The device thus described performs splitter/combiner functionswith connector 40-0 being a main connector and with connectors 40-1through 40-8 being branch connectors. In other words, a signal admittedto connector 40-0 is split into eight equal signals passed to connectors40-1 through 40-8. Further, the main signal may be monitored throughforward connector 41.

[0060] As shown in the drawings, all of the connectors 40-0-40-8 areconnected to the connection locations 48-0 -48-8 via coaxial cables 70-0through 70-8 such that the ground shield of the coaxial cable iselectrically connected to the ground shield of the connectors 40-0through 40-8, respectively, as well as connected to the conductive layer44 c.

[0061] In RF circuits, impedance matching is critical. The parallelrelation of the electrically conductive layer 44 c to the sidewall 18 ofthe housing 12 presents a small capacitance. Further, the spacedrelation of the circuit paths 53 to the opposite sidewall 20 presents aminute capacitance. Capacitance between the housing and the circuitcomponents are referred to as “parasitic reactants”. Further, there isnatural capacitance or reactance of components on the circuit board 44.The pathways 53 are tuned to balance the capacitance. The pathways 53are tuned by adjusting the size of the circuit pathways 53 such thatthey present an inductance selected to balance the parasitic reactancesand the circuit board reactances. It will be appreciated that sizingcircuit pathways to present a desired impedance is well known in theart. Also, the cables 70-0 through 70-8 are routed between the groundsurface 44 c of the circuit board 44 and its opposing sidewall 18 of thehousing 12. By routing the cables 70-8, 70-8 on this side of the circuitboard 44 and avoiding placing the cables adjacent any of the circuitcomponents or circuit pathways, undesirable reactances are avoided.

[0062] With the structure thus described, the desired circuit functionis attained in a modular format. Further, in addition to impedancematching circuit components, the selection and arrangement of componentspermits a high performance module with impedance matching throughout andwith desired flatness of a signal across the broad band frequency range.

[0063] As shown in the drawings, the forward ledge 34 includes aplurality of resilient spring contacts 35 mounted on the ledge 34 andpositioned to swipe against the electrically conductive layer 44 c asthe cover 14 is placed on to the housing to insure enhanced electricalcontact between the conductive layer 44 c and the cover 14 so that allelements are grounded when coaxial cables are connected to the rearconnectors.

[0064] To further protect the signal, the front cover 100 is provided onfront end 14 to cover and enclosed all attenuator plugs 64-1-64-8extending through holes 36. The cover 100 prevents EMI interferencewhich would otherwise occur by uncovered plugs 64 extending throughholes 36.

[0065] The foregoing discussion with respect to FIGS. 1-11 described anembodiment of the present invention for an RF module having splitterfunctions and monitor functions. FIGS. 12-18 illustrate the invention ina different embodiment for an equalizer circuit. In an equalizercircuit, an equalizer component is used to provide the same degree ofattenuation at the extremes of the RF bandwidth. Elements similarlynumbered with respect to the previously described embodiment arenumbered similar in FIGS. 12-18 with the addition of an apostrophe todistinguish between the embodiments.

[0066] In FIG. 12, a module 10′ includes a housing having a base 18′ andsidewalls 22′, 24′. The module 10′ further includes a front face 14′ anda rear face 16′. A side cover 20′ closes the module 10′.

[0067] As in the previously described embodiment, the present inventionincorporates a printed circuit board 44′ containing circuit components.The circuit board 44′ is maintained in parallel spaced relation betweenthe sidewall 20′ and the lower sidewall 18′ by support posts 42′ andassociated screws 43′.

[0068] For the equalizer circuit, the circuit components include adirectional coupler 50′ and an equalizer component 64′ removably securedto a base member 60′. The 64′ may be removed or replaced through anopening 36′ in the forward wall 14′.

[0069] The rear wall 16′ contains coax connectors 40-0′, 40-1′ and40-2′. Coaxial cables (not shown) extend from the coax connectors 40-0′through 40-2′ and beneath the printed circuit board 44′ in a manneridentical with that previously described. Further, as in the previousembodiment, the circuit board 44′ contains an electrically conductivelayer opposing and electrically connected to surface 18′. Also, thecircuit paths on the upper surface of the board 44′ are provided tobalance impedances as previously described.

[0070] The coaxial cables will extend between the board 44′ and thesurface 18′ for reasons previously discussed. The circuit paths on theboard 44′ are disposed such that an incoming circuit from incomingsignal from 40-0′ is passed to the equalizer and then to the directionalcoupler 50′. Further, the separate incoming signal can be passed fromconnector 40-1′ to directional coupler 50′ encoupled with the signalfrom the equalizer 64′ with the coupled signal passed to the outputconnector 40-2′. A support 51′ is mounted within the interior of thehousing to guide equalizer 64′ toward base member 60′ in requiredalignment. As with the previous embodiment, a cover 100′ covers thefront face 14′ together with a gasket 102′ to prevent EMI.

[0071] All other features of the module 10′ are similar to the module 10including the external dimensions and tabs of the module such that amodule 10′ may be interchangeable in a chassis with a module 10.Further, the module 10′ has the same impedance matching and parasiticreactance compensation previously mentioned with respect to module 10.As a result, the invention of module 10 is incorporated into module 10′with module 10′ showing a specific embodiment of the invention for usewith an equalizer component. It will be appreciated that equalizercomponents 64′ are commercially available items. An example of such isproduct number G75-000 of ADC Broadband Communications Division, 999Research Parkway, Meridan, Conn. 06450.

[0072] FIGS. 19-25 illustrate a third embodiment of the presentinvention for use in a 6-port directional coupler. The directionalcouplers are used to split or add multiple signals. Elements similarlynumbered with respect to the previously described embodiments arenumbered similarly in FIGS. 19-25 with the addition of a doubleapostrophe to distinguish between the embodiments.

[0073] In FIGS. 19-25, a module 10″ includes a housing 12″ having a base18″ and sidewalls 22″, 24″. The module 10″ further includes a front face14″ and a rear face 16″. A side cover 20″ closes the module 10″.

[0074] As in the previously described embodiments, the present inventionincorporates a printed circuit board 44″ containing circuit components.The printed circuit board 44″ is maintained in parallel spaced relationbetween the sidewalls 20″ and the lower sidewall 18″ by support post 42″and associated screws 43″.

[0075] The circuit components include six directional couplers 50-1″through 50-6″, each with individually associated attenuator plugs 64-1″through 64-6″ which are removably secured to individual base members60-1″ through 60-6″. Each of the attenuator plugs 64-1″ through 64-6″may be removed or replaced through openings 36″ in the forward wall 14″.

[0076] The rear wall 16″ contains coax connectors 40-0″ through 40-6″.Coaxial cables (not shown in FIGS.) extend from each of the coaxconnectors 40-0″ through 40-6″ and beneath the printed circuit board 44″in a manner identical with that described with reference to the firstpreferred embodiment of FIG. 1. Further, as in the previous embodiment,circuit board 44″ contains an electrically conductive layer opposing andelectrically connected to surface 18″. Also, the circuit paths on theupper surface of the board 44″ are provided to balance impedances aspreviously described.

[0077] The coaxial cables will extend between the board 44″ and thesurface 18″ for reasons previously discussed. The circuit paths on theboard 44″ are disposed such that six incoming signals may be separatelyconnected to each of connectors 40-1″ through 40-6″ and passed throughthe individual attenuators 64-1″ through 64-6″ into the directionalcouplers 50-1″ through 50-6″ where the six signals will be joined into acommon output signal passed to connector 40-0″. As with the previousembodiment, a cover 100″ covers the front face 14″ together with agasket 102″ to prevent EMI.

[0078] All of the features of the module 10″ are similar to the modules10, 10′ including the external dimensions and tabs of the modules suchthat the modules 10″, 10′ and 10 may be interchangeable in a commonchassis. Further, the module 10″ has the same impedance matching andparasitic reactants compensation previously mentioned with respect tomodule 10. As a result, the invention of modules 10 and 10′ isincorporated into module 10″ with module 10″ showing a specificembodiment of the invention for use with a 6-port directional couplercircuit.

[0079]FIG. 26 shows a first chassis 200 for housing a plurality ofmodules 10. The chassis 200 includes horizontally spaced apart sidewalls202, 204 and vertically spaced apart top and bottom walls 206, 208. Thetop and bottom walls 206, 208 are spaced apart by a distancesubstantially equal to a distance between the end walls 22, 24 of themodule 10.

[0080] Each of the top and bottom walls 206, 208 includes a plurality ofvertically aligned grooves 210. The grooves 210 are sized to slidablyreceive the projecting flanges 20 a, 20 b of the module 10 such that amodule may be slidably inserted into the frame 200 with the modules 10vertically positioned. In the embodiment shown, there are 12 pairs ofvertically aligned grooves 210 such that 12 modules may be inserted intothe frame 200. Since the flanges 20 a, 20 b of the modules 10 are offsetfrom a longitudinal plane of the module 10, the grooves 210 are offsetfrom module receiving spaces so that the entire open space between thesidewalls of the frame may be filled with modules. Also, the grooves 210are spaced apart a distance selected such that as modules are slidablyinserted into the frame, adjacent modules are positioned with a smallspacing between opposing sidewalls of adjacent modules 10.

[0081] Locking screws 214 are provided on the projecting tabs 14 a, 14 bof the front walls 14 of the modules 10. Corresponding threaded lockingholes 216 are provided on both the top and bottom walls 206, 208 of theframe 200. The screws 214 are not centrally positioned on the tabs 14 a,14 b. Instead, they are laterally offset from a central longitudinalaxis of the front wall 14. The holes 216 are similarly offset to requirethat a module 10 be placed in the frame 200 in a desired orientation andcannot be flipped 180° to be inserted in an undesired orientation. Theframe 200 also includes a hinged cover 218 which preferably istransparent to permit an operator to inspect the interior. Cablemanagement brackets 220 are provided on the rear of the chassis 200.

[0082] From time to time, a customer or purchaser of the modules 10 maydesire to hold the modules 10 in a horizontal alignment rather than thevertical alignment of FIG. 26. An alternative chassis 200′ is shown inFIG. 27 for holding the modules 10 in a horizontal alignment. In FIG.27, the chassis 200′ includes horizontally spaced apart sidewalls 202′,204′ and vertically spaced apart top and bottom walls 206′, 208′. Anintermediate wall 209′ is provided midway and parallel to side walls202′, 204′. The distance between either of side walls 202′, 204′ andmidwall 209′ is equal to a distance between the end walls 22, 24 of themodule 10.

[0083] Each of the sidewalls 202′, 204′ and the midwall 209′ include aplurality of horizontally aligned grooves 210′. The grooves 210′ aresized to slidably receive the projecting flanges 20 a, 20 b of themodule 10 such that a module may be slidably inserted into the frame200′ with the module 10 horizontally positioned.

[0084] In the embodiment shown in FIG. 27, there are six pairs ofhorizontally aligned grooves 210′ on both sides of the center wall 209′such that the frame 200′ can contain a total of 12 modules. As a result,chassis 200 and 200′ give an operator the opportunity to contain theexact same number of modules 10 in either a horizontal or a verticalalignment as the operator may select.

[0085] Also, the locking screws 214 of the modules are aligned withlocking holes 216′ on the side walls 202′, 204′ and mid wall 209′. Sincethe screw 214 are not centrally positioned on tabs 14 a, 14 b, and theholes 216′ are not centrally positioned in modules receiving spaces, amodule 10 must be placed in the frame 200 in a desired orientation andcannot be flipped 180° to an undesired orientation. As in the embodimentof FIG. 26, the frame 200′ of FIG. 27 includes a hinged cover 218′ andcable management brackets 220′.

[0086] Finally, FIG. 28 shows a chassis 200″ which may be used in theevent that an operator does not wish to have a combined total of 12modules but instead only wishes to have a fewer number of modules.Chassis 200′ retains two modules 10 in side-by-side horizontal alignmentand includes mounting brackets 201 for mounting to a frame structure sothat an operator can elect to mount pairs of modules at a time ratherthan twelve modules 10. Frame 200″ is similar to frame 200′ in that ithas an intermediate wall 209″ between side walls 202″ and 204″ with thelocking screws 214 received within holes (not shown) of walls 202″, 204″and 209″.

What is claimed is:
 1. A module for containing a circuit for performing discrete circuit functions on a radio frequency signal, said module comprising: a housing of electrically conductive material defining an enclosed interior; said housing having a front face and an opposite rear face separated by opposite sidewalls and opposite end walls; a plurality of coax connectors secured to said rear face with an outer shield of said connectors electrically coupled to said housing; a circuit board contained within said interior and positioned generally parallel to and spaced between said sidewalls; said circuit board having a component side opposing a first of said sidewalls and a ground side opposing a second of said sidewalls; said ground side including a layer of electrically conductive material electrically connected to said housing; a plurality of coax cable connection locations on said ground side of said circuit board, each of said coax cable connections including a ground connection for connecting ground shields of coax cables to said layer of electrically conductive material; said component side of said circuit board including a plurality of circuit components interconnected with one another and with said coax cable connection locations through a plurality of circuit paths; a plurality of coax cables disposed within said interior and connected to individual ones of said coax connectors and said coax cable connection locations, each of said coax cables having ground shields connected to said outer shields of said connectors and to said ground connections of said coax cable connection locations; and said plurality of cables routed for said cables to be disposed between said ground side of said circuit board and said second of said sidewalls.
 2. A module according to claim 1 wherein said circuit paths are sized to have an impedance selected to balance a parasitic reactance between said circuit board and said housing.
 3. A module according to claim 1 wherein said plurality of components includes splitter components for receiving a main signal from one of said coax connection locations and dividing said main signal into a plurality of branch signals delivered along said circuit paths to individual remaining ones of said coax connection locations.
 4. A module according to claim 1 wherein said splitters components are adapted to act as combiner components for receiving said plurality of branch signals from said individual ones of said coax connection locations and combining said branch signals into said main signal delivered along one of said circuit paths to said one of said coax connection locations.
 5. A module according to claim 3 wherein said splitter components includes at least a first splitter and a second splitter connected in series.
 6. A module according to claim 5 wherein said splitter components includes a third splitter connected in series with said first splitter and in parallel with said second splitter.
 7. A module according to claim 3 wherein said circuit components include a plurality of attenuators associated with individual ones of said branch circuits.
 8. A module according to claim 7 wherein said attenuators include a variable attenuator component for varying an amount of attenuation of said attenuators.
 9. A module according to claim 8 wherein said attenuators includes a first attenuator component mounted on said component side of said circuit board and said variable attenuator component removably secured to said first component with said variable attenuator component selected for a fixed desired attenuation.
 10. A module according to claim 9 wherein: said attenuators are positioned adjacent said front face; said front face having an opening sized to pass said second variable attenuator component through said front face; an electrically conductive cover releasably secured to said front face and sized to cover said opening.
 11. A module according to claim 10 wherein said cover and said front face include an electrically conductive, mechanically deformable seal.
 12. A module according to claim 1 wherein said front face is removable from a remainder of said housing and includes electrically conductive, mechanically resilient conductors extending between said front face and said layer of conductive material.
 13. A module according to claim 12 wherein said front face includes a protruding ledge disposed to support a leading edge of said circuit card.
 14. A module according to claim 3 wherein said circuit components include a directional coupler for diverting a portion of said main signal to a connector location connected to a monitor coax connector.
 15. A module according to claim 14 wherein said monitor coax connector is exposed on said front face.
 16. A module according to claim 1 wherein said circuit components include a directional coupler.
 17. A module according to claim 16 wherein said components include an equalizer for equalizing a radio frequency signal along a frequency range.
 18. A module according to claim 17 wherein said equalizer includes a first equalizer component mounted on said component side of said circuit board and a variable equalizer component removably secured to said first component with said variable equalizer component selected for a fixed desired radio frequency equalization.
 19. A module according to claim 18 wherein: said equalizer is positioned adjacent said front face; said front face having an opening sized to pass said second variable equalizer component through said front face; an electrically conductive cover releasably secured to said front face and sized to cover said opening.
 20. A chassis and module combination for permitting selective housing of a plurality of modules containing radio frequency circuits, said combination comprising: A. a plurality of modules each having: a housing of electrically conductive material defining an enclosed interior; said housing having a front face and an opposite rear face separated by opposite sidewalls and opposite end walls, with each of said faces and sidewalls being of predetermined dimension and with said sidewalls being parallel to one another; a plurality of coax connectors secured to said rear face with an outer shield of said connectors electrically coupled to said housing; a circuit board contained within said interior and positioned generally parallel to and spaced between said sidewalls; said circuit board having a component side opposing a first of said sidewalls and a ground side opposing a second of said sidewalls; said ground side including a layer of electrically conductive material electrically connected to said housing; a plurality of coax cable connection locations on said circuit board, each of said coax cable connections including a ground connection for connecting ground shields of coax cables to said layer of electrically conductive material; said component side of said circuit board including a plurality of circuit components interconnected with one another and with said coax cable connection locations through a plurality of circuit paths; said circuit components selected to perform a circuit function on a radio frequency signal supplied to one of said connectors and to provide an output radio frequency signal to a remainder of said connectors; a plurality of coax cables disposed within said interior and connected to individual ones of said coax connectors and said coax cable connection locations, each of said coax cables having ground shields connected to said outer shields of said connectors and to said ground connections of said coax cable connection locations; each of said end walls having a projecting flange extending in a common plane generally parallel to said sidewalls and with said common plane offset from a central longitudinal axis of said housing; said front face including end portions extending beyond each of said end walls; a locking member secured to each of said end portions and having a locking end extending through a rear surface of said end portions; at least one of said locking members positioned offset from a longitudinal axis of said front face; B. a first chassis having: a first chassis frame including horizontally spaced apart first sidewalls and vertically spaced apart first top and bottom walls with said first top and bottom walls spaced apart by a distance substantially equal to a distance between said end walls of said modules; each of said first top and bottom walls including a plurality of vertically aligned first grooves sized to slidably receive said projecting flanges; said first grooves spaced along said first top and bottom walls for a predetermined number of said modules to be slidably received within said first frame in a vertical orientation with said longitudinal axis of said front face vertically disposed and with opposing sidewalls of adjacent modules narrowly spaced apart; a plurality of first mating lock members on each of said first top and bottom walls and positioned to mate with said locking members of said modules when said modules are received within said first frame in a predetermined orientation and with said flanges received within said first grooves; C. a second chassis having: a second chassis frame including horizontally spaced apart second sidewalls and vertically spaced apart second top and bottom walls; an intermediate wall extending vertically between said second top and bottom walls and centrally positioned between said second sidewalls with said intermediate wall dividing said second frame into a left column and a right column; said second sidewalls spaced from said intermediate wall by a distance substantially equal to a distance between said end walls of said modules; each of said second sidewalls and intermediate wall including a plurality of horizontally aligned second grooves sized to slidably receive said projecting flanges; said second grooves spaced along said second sidewalls and said intermediate wall for half of said predetermined number of said modules to be slidably received within said left column of said second frame in a horizontal orientation with said longitudinal axis of said front face horizontally disposed and with opposing sidewalls of adjacent modules narrowly spaced apart; said second grooves further spaced along said second sidewalls and said intermediate wall for half of said predetermined number of said modules to be slidably received within said right column of said second frame in a horizontal orientation with said longitudinal axis of said front face horizontally disposed and with opposing sidewalls of adjacent modules narrowly spaced apart; and a plurality of second mating lock members on each of said second sidewalls and intermediate wall and positioned to mate with said locking members of said modules when said modules are received within said second frame in a predetermined orientation and with said flanges received within said second grooves. 